1. Field of the Invention
This invention relates to a fitting for use in providing access to the interior of a pipe. The invention is particularly applicable to the field of art relating to apparatus for working on a pipeline having liquid or gas therein by providing means of securing access to the interior of the pipeline without the escape of such liquid or gas and without the necessity of first draining or depressurizing the pipeline. The invention is related to apparatus which can be secured to the exterior of a pipe and thereafter an opening formed in the pipe to provide a passageway through which a plugging device may be inserted into the interior of the pipe to close off the pipe against liquid or gas flow.
2. Description of the Prior Art
A known technique in the maintenance of pipelines is the use of apparatus for achieving communication with the interior of the pipeline without the necessity of draining it of liquids or gases. For this purpose it has been a known practice to provide tapping devices which may be secured to the outside of a pipeline. These tapping devices typically include a branch fitting welded or bolted to a pipeline. By means of a valving structure secured to the branch fitting, a tapping tool may be used to drill a hole in the line, thus providing communication between the interior of the line and the branch so that fluid flow may be continued through the branch.
While the apparatus of the prior art has worked satisfactorily to achieve the intended results, known techniques, particularly when it is necessary to close off a pipeline to prevent fluid or gases therein from escaping while repairs are conducted on the line, require apparatus in which a number of steps must be employed, including the use of a valving structure.
The reason that a sequence of a relatively large number of steps is necessary is that all of the present devices require both the hole forming operation and the plugging operation to be carried out along the same axial passageway. This means that equipment used for providing the opening in the pipeline must be withdrawn and replaced with the plugging equipment. This requires some type of valving function intermediate these steps. Otherwise the interior of the pipeline is exposed for the discharge of contents.
The present invention is directed towards a dual function fitting in which access is provided to the interior of a pipeline without exposing the contents of the pipeline for discharge to the environment and in which the operations of forming an opening in the pipeline are carried out in a separate compartment compared to the operations for plugging or other efforts in the pipeline. The present device provides a unique fitting for use on pipelines in which all of the apparatus required for forming an opening in a pipeline and for subsequently plugging the pipeline can be carried in a single structure in which no valving function is required between the step of drilling an opening in a pipeline and the step of plugging the pipeline by inerting a plugging member through the opening having been formed in the pipeline.
It is therefore an object of this invention to provide a new type of fitting for use in maintenance and repair of pipelines.
More particularly, an object of this invention is to provide a dual branch fitting for use on a pipeline in which, after the fitting is attached to the exterior of a pipeline, an opening may be formed in the pipeline, by means in one branch of the fitting and subsequently, operations carried out within the pipeline through the formed opening by means extending from the other branch of the fitting.
These general objects as well as other and more specific objects and advantages of the invention will be set out in greater detail in conjunction with the attached drawings.
For an indication of the state of the art as to other similar devices relating to the subject matter of this invention, reference may be had to the following United States patents:
Myll U.S. Pat. No. 3,156,490, Minchhoff U.S. Pat. No. 3,756,261, Witter U.S. Pat. No. 4,015,321, Freeman U.S. Pat. No. 4,054,978, DeHoff U.S. Pat. No. 4,067,353, Bills U.S. Pat. No. 4,103,940, and Sakamoto et al. U.S. Pat. No. 4,243,217.